How can I access, edit, add and remove Metaballs in Edit Mode with Animation Nodes?
You can use a simple script as follows, you access the required metaball data block by name, clear its balls, and add new metaballs and edit their attributes like location and radius:



mball = bpy.data.metaballs[name]
mball.elements.clear()
for v, r in zip(locations, radii):
    ele = mball.elements.new()
    ele.co = v
    ele.radius = r


The API describe the possible attributes per ball.